U.S. patent number 3,749,158 [Application Number 05/091,242] was granted by the patent office on 1973-07-31 for heat exchange apparatus for the utilisation of the heat content of exhaust gases.
This patent grant is currently assigned to Magyar Hajo-es. Invention is credited to Josef Szabo, Laszlo Szucs.
United States Patent |
3,749,158 |
Szabo , et al. |
July 31, 1973 |
HEAT EXCHANGE APPARATUS FOR THE UTILISATION OF THE HEAT CONTENT OF
EXHAUST GASES
Abstract
Heat transfer apparatus for the utilization of the heat content
of exhaust gases includes two heat-exchangers linked by a closed
circuit in which an intermediate medium circulates. There is a
special device for restricting or stopping the flow of the
intermediate medium which receives heat in one of the
heat-exchangers from the hot exhaust gases and transfers it to the
heat-receiving medium in the other heat-exchanger.
Inventors: |
Szabo; Josef (Budapest,
HU), Szucs; Laszlo (Budapest, HU) |
Assignee: |
Magyar Hajo-es (Budapest,
HU)
|
Family
ID: |
22226765 |
Appl.
No.: |
05/091,242 |
Filed: |
November 20, 1970 |
Current U.S.
Class: |
165/96;
165/104.27; 237/9R; 165/104.21; 165/909; 237/68 |
Current CPC
Class: |
F28D
19/00 (20130101); F28D 21/0003 (20130101); F24D
3/00 (20130101); F28F 27/00 (20130101); Y10S
165/909 (20130101) |
Current International
Class: |
F28F
27/00 (20060101); F24D 3/00 (20060101); F28D
19/00 (20060101); F28d 015/00 (); F24d
001/00 () |
Field of
Search: |
;165/105,110,113,96
;123/41.27,41.54 ;237/9,67,68 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Davis, Jr.; Albert W.
Claims
We claim:
1. Heat transfer apparatus for the utilization of the heat content
of exhaust gases, including a first heat-exchanger placed in the
path of the exhaust gases, a second heat-exchanger, means for
supplying a heat-receiving medium to the second heat-exchanger, a
closed flow circuit connecting said heat-exchangers, a
heat-exchange medium circulating, in operation, in said circuit so
as to be heated in the first heat-exchanger and cooled in the
second heat-exchanger, deaerating means for the second
heat-exchanger, a device for restricting the flow of liquid
heat-exchange medium between said heat-exchangers, said device
being in the form of an inverted U-tube having an uprising limb and
a downcoming limb, said uprising limb being connected at its top to
the second heat-exchanger, and a heater for said uprising limb.
2. Apparatus as claimed in claim 1 wherein the deaerating means
includes a coolable container, cooling means for said container,
and flow lock, the said container being connected to the second
heat-exchanger both directly and by way of said flow lock.
3. Apparatus as claimed in claim 1, said heater being disposed at
the lower end of said uprising limb whereby said uprising limb
serves as a vapor lift.
Description
The invention concerns heat transfer apparatus for the utilization
of the heat content of exhaust gases.
In heating technology there often occurs the task of utilization of
hot gases in inexpensive and well controllable apparatus for the
purpose of heating or evaporating some heat-receiving medium
(usually water).
Special problems arise when the production of the hot gases is not
in step with the criterion for the intake of heat of the
heat-receiving medium. This is the case where e.g. the hot gases
are exhaust gases and the heat-receiving medium is water to be used
for heating; it often occurs that at a given instant there is no
actual need for heating, yet exhaust gases are still being formed.
In such cases the known regulating methods either cannot be used or
require very expensive equipment.
From the point of view of apparatus regulation, there is known a
solution wherein the heat intake of the heat-receiving medium is
regulated by varying the quantity and/or temperature of the exhaust
gases; further, another solution is known, wherein the quantity of
steam produced is regulated by varying the rate of the surface area
that is being exposed or "flooded" (in this case, the
heat-receiving medium is evaporated in a large volume apparatus by
being directly heated by the hot gases).
Regulation by varying the quantity of gases can be effected, in the
above-mentioned case, by a drawing-off method, but this can only be
done in principle, for the required sealing device always leak and
the leakage of hot gases results in either an impermissible
increase in pressure on the "secondary" side, or in the
impermissible heating or evaporation of the water flowing through
the apparatus. Moreover, sealing devices suitable for drawing off
gases are expensive.
In the case of regulation by varying the area of exposure the
heat-exchanging surfaces very rapidly become covered by scales,
since all heat-receiving medium coming into contact with the
heating surface is evaporated, therefore there is no rinsing, and
furthermore the surfaces become hot by being in contact with hot
smoke gases. Because of the rapidly deteriorating heat transfer
efficiency, extremely large surfaces must be provided and they must
often be cleaned, and also associated conduits are often
damaged.
There is a further known solution wherein the hot gases serve to
evaporate some intermediate medium, and the heat-receiving medium
to be heated or evaporated takes up its heat in a condenser for the
intermediate medium. In this case the hitherto known method of
control consists of the heat-receiving medium being allowed to take
up all the heat it can from the hot gases, but some third,
auxiliary cooling medium is provided promptly to draw off excess
heat at a further heat-exchange surface from the heat-receiving
medium.
This last solution was conceived to obviate the drawbacks of the
long known, practically "classic," solutions of the problem
described above, and gives superior results. However, a grave
disadvantage of even this solution is that it requires a third
cooling medium to operate it, also it is complicated and expensive,
requiring a three-way heat-exchange apparatus for its
achievement.
An intermediate medium is also used for heat transfer in the
so-called Schmidt-Hardtmann boiler, well-known in boiler
construction. However, as this boiler has its own combustion
apparatus, and naturally regulation is here effected by controlling
the combustion apparatus.
It is to be noted that with this type of boiler it is an essential
condition, for basic security reasons, that there should be no
flow-restricting means in the circulation path of the intermediate
medium.
This invention seeks the elimination of the above disadvantages and
the provision of a heat transfer apparatus for the utilization of
the heat-content in exhaust gases, wherein steam production is
controllable by very simple means and is terminable even without
the stoppage of flow of exhaust gases. The invention is based on
the recognition that the above aim may be achieved if the
utilization of the heat of the exhaust gases is effected by an
intermediate medium, and a specially formed fluid flow restricting
or terminating device is inserted into the circulation path of the
intermediate medium.
According therefore to the present invention, there is provided
heat transfer apparatus for the utilization of the heat content of
exhaust gases, including a first heat-exchanger adapted to have an
intermediate medium supplied thereto and placed in the path of the
exhaust gases for the evaporation of the intermediate medium, said
first heat-exchanger being connected in a closed fluid flow circuit
to a second heat-exchanger which is adapted to condense the vapour
of the intermediate medium in heat exchange with a heat-receiving
medium and which is provided with a deaerating means, there being
ducting between the two heat exchanges in which is disposed a
device for the restriction or elimination of the flow of liquid
between said heat-exchangers.
In an advantageous preferred embodiment of this invention the air
exhausting or deaerating means is a gas container provided with
natural or artificial cooling means which is connected to the
condenser heat exchanger partly directly and partly via a flow
seal.
The invention is described in detail, by way of examples, with
reference to the accompanying drawings, wherein:
FIG. 1 is a schematic circuit diagram of a preferred embodiment of
the apparatus according to this invention.
FIG. 2 is a schematic diagram of a modified embodiment of the
apparatus according to this invention,
FIGS. 3 and 4 are further schematic illustrations of preferred
embodiments of the apparatus according to this invention, and
FIG. 5 is a still further schematic illustration of preferred
embodiments for assembling the apparatus according to this
invention.
Referring to the drawings, the FIG. 1 apparatus incorporates an
intermediate medium in a closed circuit in which are arranged an
evaporating heat exchanger 11 and a condensing heat exchanger 9. An
air exhausting or deaerating means 5 is connected to the condensing
heat exchanger 9, while between the condensing heat exchanger 9 and
the evaporating heat exchanger 11 is inserted a device 1 for
restricting or stopping the fluid flow. Examples of the
construction of the device 1 are shown in FIGS. 3 and 4, and are
explained with reference thereto.
In the case of the FIG. 1 embodiment, in operation exhaust gases 12
evaporate a completely pure intermediate medium in the heat
exchanger 11, and the vapour 2 of the intermediate medium is passed
to the condensing heat exchanger 9 by way of ducting 22, whereby to
heat or evaporate the heat-receiving medium 3 which flows through
the heat exchanger 9.
Having regard to the fact that the intermediate medium is
completely pure, there is no need to fear scaling-up due to
imperfect exposure, therefore problems connected with regulating
the degree of exposure (or flooding). When there is no further need
for the warming up or evaporating the intermediate medium 3, the
flow of the intermediate medium is stopped by means of device 1,
whereupon the supply of evaporating and heat exchanging liquid is
interrupted and heat transfer through the intermediate medium
ceases.
For the correct operation of the apparatus, the condensing heat
exchanger 9 of the intermediate medium must be deaerated.
Deaeration may be achieved by a per se known method: on starting up
of the apparatus, when the pressure of the intermediate medium
still esceeds the atmospheric pressure, the deaerating means 5 is
actuated. The disadvantage of this method is that manual actuation
is required for the deaerating means 5 which is preferably in the
form of a simple tap; also with the air a portion of the vapor of
the intermediate medium is also removed from the system which thus
requires frequent topping-up.
Deaeration may advantageously be obtained by the embodiment shown
in FIG. 2. Here the deaerating means 5 is constituted by a gas
container 4 having a natural or artificial cooler 6; the upper part
of the container being connected by way of a duct 7 to the
deaerating outlet of heat exchanger 9, while its lower part is
connected to the condensing heat exchanger 9 by way of a fluid lock
8. While the system is inoperative, pressures are small and
non-condensing gases can be found everywhere. However, as soon as
steam production commences, i.e. flow of the heat-receiving medium
3 through the heat exchanger 9 begins, the pressure in the circuit
of the intermediate medium rises and condensation of the
intermediate medium starts up also. The condensation of the
intermediate medium terminates, however, in the cooled gas
container 4. A steam-vapour mixture arrives in the gas container 4,
but only liquid leaves it, and for this reason all non-condensing
gases to be found in the system collect here; that is to say, the
condensing heat exchanger 9 is deaerated.
The liquid supply to the heat exchange surface heated by hot smoke
gases can be regulated by known means, e.g. by valves. There is the
attendant disadvantage, however, that in time all valves develop
leaks. Thus the heating surface will receive liquid even when the
valves are closed. This has the result that, when cooling is
absent, the pressure of the intermediate medium soon becomes
impermessibly great. The valves, cocks, etc. therefore require
constant maintenance and care, which in itself is a disadvantage,
and further this solution has the harmful consequence that each
repair involves loss of intermediate medium as well, thus
necessitating topping-up.
All these disadvantages can be eliminated if the following
procedure is employed.
One mode of construction of the device 1 for restricting or
stopping the fluid flow is shown in FIG. 3. Here the device 1 is in
the form of an inverted U-shaped tube 14, 17 whose upper part is
constituted by a chamber incorporating a baffle 21 and of the
U-shaped tube 14, 17 is such that normally the flow of intermediate
medium cannot penetrate therethrough. In limb 14 of the U-shaped
tube 14, 17 a heating means 16 is disposed.
When it is desired to start evaporating the medium 3 the heater 16
is switched on, which results in the formation of steam bubbles in
the limb 14. The liquid level will then rise and will tumble over
the baffle 21 to pass to the evaporating heat exchanger 11, wherein
it evaporates and thus the circular flow of the intermediate medium
begins and is maintained while the heater 16 remains in operation.
The duct 18 serves to pass steam generated by the heater 16 to the
condensing heat exchanger 9.
Another example of construction of the device 1 embodied in the
apparatus according to the invention can be seen in FIG. 4. Here
the inverted U-shaped tube 14, 17 has a vessel 23 connected to its
uprising limb 14. The vessel 23 is provided with a heater 25 and/or
a cooler 26, and is connected to the condensing heat exchanger 9 by
way of a restrictor 24. In the apparatus according to this
embodiment the device 1 operates as follows. When the vessel 23 is
heated by heater 25, the steam formed displaces the liquid,
consequently the quantity of liquid in limb 14 of the U-shaped tube
increases, reaches the top of the tube, and flows over it, i.e. the
flow of the intermediate medium into the evaporating heat exchanger
11 commences.
When the vessel 23 is cooled, which may be by natural cooling also,
then the steam condenses and the vessel 23 fills with liquid. Thus
the liquid level falls in the limb 14 of the U-shaped tube and flow
of the intermediate medium into the evaporating heat exchanger
ceases.
A further possible solution for the apparatus may be obtained by
allowing a part of the steam generated in vessel 23 by heater 25
continuously to pass out of the system via restrictor 24. However,
when the heater 25 is on, a part of the steam generated cannot pass
out through the restrictor 24 and no fresh steam is generated,
consequently the vessel 23 will once more fill up with liquid.
The restrictor 24 and the cooler 26 may be employed simultaneously.
The apparatus according to the invention can also be realised by
employing cooler 26 and restrictor 24 only. In this case the
cooler, as it were, sucks the liquid into the vessel 23 and
cessation of cooling results in the vessel 23 filling up with steam
via restrictor 24, and the liquid level will rise in the tube limb
14.
The apparatus according to this invention provides, beyond the
above-described favourable properties, special possibilities for
connecting up its integers which in turn become the source of
further advantages. In the case of apparatus where considerable
energy is required for the heating of the liquid flow restricting
means, the following combined apparatus may be constructed (see
FIG. 5).
The fundamental portion of the apparatus is the apparatus according
to this invention shown in FIG. 3 or FIG. 4. To this is connected a
considerably smaller apparatus, also according to this invention,
for utilizing the heat content of exhaust gases in such a manner
that the heater 25 of the liquid flow restricting device of the
fundamental, large output apparatus and the condenser of the small
output apparatus together constitute a common heat transfer device:
on the side of the surface of the heat transfer device the steam of
the intermediate medium of the small output apparatus condenses, on
the other side takes place the heating required for the operation
of the liquid flow restricting device of the large output
apparatus.
Regulation of the combined plant is similar to that of the simple
apparatus: when the heating of the liquid flow restricting device
of the small output apparatus is switched on, then this will
furnish heat for the liquid flow restricting device of the large
output apparatus, and the large output apparatus commences its
operation. Stopping operation is effected by switching off the
heating in the small output apparatus By way of example, a
combination is shown in FIG. 5 where both the small output and
large output apparatus is constructed in accordance with FIG. 4.
However, there is no obstacle to either apparatus being constructed
differently, e.g. according to the example of embodiment shown in
FIG. 3.
The advantage of the apparatus is self-evident: the regulation and
stopping described in the introduction can take place under the
same favourable conditions, but with the expenditure of
considerably smaller auxiliary energy, which is advantageous for
large outputs.
* * * * *